New energy vehicles have been widely prompted all over world, but more improvements are required for them to replace fuel vehicles completely. For example, problems such as short driving distance, high cost of battery packs, and reliability of battery packs needs to be further addressed. For the above problems, higher requirements are placed on the core component, i.e., power battery, of electric vehicles, for example, the power battery is required to achieve a higher energy density, a lower cost, etc.
Currently, the power battery generally adopts a square hard case structure, the power battery case includes a case and a top cap assembly, and the power battery case provides a sealed space for accommodating electrode assembly and electrolyte. The electric energy of the electrode assembly is extracted to outside of the sealed space through the electrode terminal of the top cap assembly. In the existing top cap assembly, the top cap plate is a metal plate and is provided with a through-hole, the electrode terminal is divided into a base portion and an extension portion, and the cross-sectional area of the base portion is larger than the aperture of the through-hole. During assembling, the base portion is located under the top cap plate (i.e., inside the case), and after the extension portion passes through the through-hole, the extension portion is fixed using a snap spring or riveting, and the electrode terminal is fixed onto the top cap plate in this manner. Since the base portion is located inside the case, the space utilization inside the case is reduced, thereby reducing the power density of the power battery.
Because the structure of the electrode terminal itself and the assembling procedure are complicated, not only the assembling efficiency of the secondary battery will be affected, but also after the electrode terminal is fixed onto the top cap plate, the electrode terminal and the top cap plate may disconnect due to insufficient fixing strength, which reduces the use reliability of secondary batteries.
Therefore, there is a need for a new top cap assembly of a secondary battery and second battery.